Reactive and Functional Polymers Volume One

Reactive and functional polymers are manufactured essentially from the chemical or physical modification of their precursors or by the addition of active fillers. These polymers have proven important for the development of advanced materials for different applications, and they are booming and will be a fundamental part in the future life for agricultural, energy efficiency, environmental remediation, medical devices, among others. With this chapter, we open the main topics that will be analyzed in this book.

In recent decades, there is a sustained interest in the development of drug delivery systems based on bioactive and functional polymers such as poly(propylene glycol) (PEG), poly(vinyl alcohol) (PVA), poly(lactide acid) (PLA), poly(lactic-co-glycolic acid) (PLGA), poly(ε-caprolactone) (PCL), poly(trimethylene carbonate) (PTMC) and poly(p-dioxanone) (PPDO). The U.S. Food and Drug Administration (FDA) has approved these polymers for biomedical applications due to their excellent biodegradability, biocompatibility and non-toxicity. The poly-hydroxy and -carboxy characteristics not only give them a supramolecular structure for drug loading, but also to incorporate drugs into the structure through chemical interactions. This chapter aims to present the molecular and physiochemical bases for the application of PEG and PLGA for functional delivery and controlled and targeted release of bioactive compounds.

Many reactive processes with the purpose of modifying the structure of fiber polymers are applied in textile chemistry in order to change their properties. These processes depend on the chemical nature of the polymer and the type of modification, and these aspects are discussed with respect to alkalization, chemical crosslinking with bi- and multifunctional reagents, hydrolytic processes, deposition and grafting of polymers, as well as crosslinking with urea-based reactive systems (e.g. dry cure processes). The selection of process parameters are of decisive importance for the efficient development of a desired portfolio of properties in a certain fiber-based product. This chapter aims to analyze the recent advances in reactive modification of fiber polymer materials.

The dynamic development of the automotive industry resulted in a significant increase in rubber wastes, especially end-of-life tires, which are a serious threat to the natural environment and human health. This situation has enforced the industry and academic research groups to search new and cost-effective methods for recycling waste tires. In this field of research, reactive processing and functionalization seem to be a very promising approach to extend recycling and the ‘up-cycling’ of ground tire rubber. This chapter presents recent progress in the modification of waste rubber and valorization strategies with special attention on structure-properties relationships of the products obtained.

Lignin, as one of the most abundant natural polymer compounds in wood and annual plants, has a complex chemical structure. It is fundamentally an aromatic polymer, composed of many aromatic rings with methoxyl and hydroxyl functional groups. Because of its multifunctional side groups, lignin can act as a free radical scavenger, thus acting as a natural antioxidant agent. However, extraction conditions, source species and structure affect the antioxidant activity of lignins. As a relatively safe and natural antioxidant, lignin can be used in foods, pharmaceuticals, cosmetics, and industrial materials. In this chapter, the correlation of lignin between structural characteristics and its radical scavenging capabilities, the relationship between antioxidant capacity and potential cytotoxicity, and the advances in commercial applications of lignin as an antioxidant were reviewed and analyzed.

Biobased polymers are of great interest due to the release of tension on non-renewable petroleum-based polymers for environmental concerns. However, biobased polymers usually have poor mechanical and barrier properties when used as the main component of coatings and films, but they can be improved by adding nanoscale reinforcing agents (nanoparticles - NPs or fillers), thus forming nanocomposites. The nano-sized components have a larger surface area that favors the filler-matrix interactions and the resulting material yield. For example, natural fibers from renewable plants could be used to improve the mechanical strength of the biobased composites. In addition to the mechanical properties, the optical, thermal and barrier properties are mainly effective on the selection of type or the ratio of biobased components. Biobased nanocomposites are one of the best alternatives to conventional polymer composites due to their low density, transparency, better surface properties and biodegradability, even with low filler contents. In addition, these biomaterials are also incorporated into composite films as nano-sized bio-fillers for the reinforcement or as carriers of some bioactive compounds. Therefore, nanostructures may provide antimicrobial properties, oxygen scavenging ability, enzyme immobilization or act as a temperature or oxygen sensor. The promising result of biobased functional polymer nanocomposites is shelf life extension of foods, and continuous improvements will face the future challenges. This chapter will focus on biobased materials used in nanocomposite polymers with their functional properties for food packaging applications.

Polyurethanes (PUs) are widely used for many engineering applications due to their diversified properties caused by different components and additives. Polyurethane (PU) foams, as one of the most important PU materials, are widely used in automotive parts, bedding, cushion, flotation, insulation materials and packaging. However, the PU industry relies heavily on petroleum-derived chemicals because the PU synthesis involves two major component materials (i.e. polyols and isocyanates) currently both derived from non-renewable petroleum resources. Today, the growing bioeconomy has intensified the interest of the PU industry in the development of biobased PU (BPU) foams using biopolyols (also known as bio-oils) derived from agricultural and forestry residues. This chapter aims to summarize the recent conversion technologies of forestry and agricultural residues into biopolyols, and the methods for the preparation of BPU foams by using biopolyols derived from the bio-resources.

The reactive polyesters are organic compounds based primarily on carboxyl, hydroxyl and double bond functional groups, which are produced by polycondensation or ring opening polymerization (ROP). Depending on the functional group, they can react with different types of curing agents such as 2-hydroxyalkylamides, amines, atmospheric oxygen, diisocyanates, epoxies, melamine-formaldehyde (MF) and polyols to produce the final product on an industrial scale. The polymers resulting from the polyesters and curing agents have many applications such as adhesives, coatings, composites, elastomers, foams and sealants. One of the main applications of reactive polyesters is the preparation of diisocyanate-cured PUs. There are several types of reactive PUs which are produced by reacting a polyol with an isocyanate compound. The reactive site is often isocyanate end-capped groups. However, other functional groups such as amine, carboxyl and hydroxyl can be used as the reactive site. This chapter aims to analyze reactive polyester and polyurethane.

Epoxy resin has been widely used as a coating agent within the food, aerospace, automotive, and electronics industries. However, these materials obtained from petrochemical industry cause problems related to environmental impact. In this sense, ecological epoxy resins from biodegradable natural polymers have been proposed as an alternative. Lignin is a biodegradable polymer obtained from unused plant biomass (agricultural waste or byproduct), and its use is less promising than cellulose for the manufacture of bioethanol. This chapter aims to analyze recent advances in studies of epoxy resin made from lignin.

Silicones are very useful materials that vary in their structure, reactivity and physicochemical properties, although they contain a covalent bond between silicon and the carbon atom of an organic group. Most silicone polymers are artificial because the organo-silicon bond is not found in nature. The study of the silane coupling agent has also revealed that it plays an important role in improving the durability and performance of silicone as softeners, especially the type of linear reaction. The improvements in wrinkle recovery are mainly due to the formation of an elastic silicone polymer network, which traps fibers within its matrix, which improves the fabric’s ability to recover from deformation. The results have indicated several areas of technical application for the modified fabric, such as barrier textiles with permeability control, localized modification of the mechanical properties of the fabric. The enormous opportunities in the design, synthesis and modification of the physical and chemical properties of polymers have made them the fastest growing group of materials, having great importance and possibilities for applications in cosmetology, medicine and pharmacy. In this chapter, we focus on a general description of the silicone polymers used, including polydimethylsiloxane (PDMS), with respect to their physicochemical properties and factors affecting their current applications. Finally, the use of silicone polymers as excipients in the technology of various products, e.g. skin adhesive patches and controlled drug delivery systems, are presented. The synthesis of a new class of reactive silicone resins containing vinyl and methacryloxypropyl substituents has also been discussed below. Organo-functional silanes, their chemistry, properties, uses and the main laboratory experiments that may also be of interest to the food and beverage industry.

With a history of almost 100 years, silicones -polymeric or oligomeric siloxanes- are well known as reliable materials with a wide range of applications, from home to the aerospace sector. The constant interest for these polymers is explained by their unique combination of properties, including chemical and physiological inertness, extreme resistance to ozone and corona discharge, film forming capacity, good thermal-oxidative and ultraviolet (UV) stability, high flexibility of the macromolecular chain, low dielectric constant, surface energy and transition temperatures, permeability to various gases, stability towards atomic oxygen and oxygen plasma, and UV-visible radiation transparency. The chemical modification of silicones is an active research area, since the attachment of several organic functional groups to the silicon atom imparts specific properties and triggers new applications. Functional siloxanes represent a bridge between siloxane and organic chemistry and combine valuable properties of silicones with reactivity and specific functions of organic moieties. In this chapter, the recent research progress in the field of functional organic siloxanes and their materials are reviewed, focusing on their applications in science and technology.

Maxillofacial prostheses are used for patients with deformities in the maxillofacial area induced by cancer, trauma or congenital defects. Different types of polymers are used in the manufacture of maxillofacial prosthesis. However, silicone elastomers are the polymers most commonly used in the maxillofacial prosthodontics because of their acceptable properties. Since maxillofacial defects create profound psychological and social difficulties in these patients, recent research focused on improving the mechanical and physical properties of silicone elastomers by using various incorporations of nano-oxide particles into the silicones. Nevertheless, the use of conventional techniques in the manufacture of maxillofacial silicones still consumes a lot of time. Silicone prostheses manufactured conventionally are also still susceptible to color degradation and change in the mechanical properties. Thus, the three-dimensional (3D) printing techniques of the maxillofacial prosthesis and the development of the printable maxillofacial prosthetic materials are of great interest. This chapter aims to analyze the novel approaches in maxillofacial prosthodontic materials, especially silicone elastomers, and recent advances in 3D printing technologies in the fabrication of maxillofacial prostheses.

Siloxane polymers (widely known as silicones) are ubiquitous materials with a wide range of applications, from pharmaceuticals and medical devices to nautical sealants and high temperature lubricants. This is due to its robust and advantageous properties as an inorganic-organic polymer, which differ widely from traditional polyolefin materials. In this chapter, the unique and remarkable properties of siloxane polymers will be analyzed, as well as the synthetic strategies for the preparation of traditional and functional silicones. An examination of the functions of siloxane polymers and copolymers in various industries, such as polyurethane foams and fluorosilicone lubricants, is presented. Traditional methods for crosslinking of siloxane polymers and the resulting coatings and bulk materials will be compared with recent advances in silicone coupling reactions, such as the Piers-Rubinsztajn and ‘click’ reactions. Finally, we examine the new emerging approach on the siloxane bond as a reactive functional group in its own right for the preparation of advanced non-stick resins and surfaces.

A comprehensive review on preparation methods of linear, branched, star and dendritic poly(hydrosiloxane)s (PHS), mainly poly(methylhydrosiloxanes) (PMHS) and Si-H functional silsesquioxanes (spherosilicates) is presented in this chapter. The most important applications of PMHS in technology of silicones, modifications of different polymers and in materials science were reviewed.